Processes for making films of oxide materials by radio frequency (RF) plasma fabrication techniques are well known to those skilled in the art; the films so produced generally have thicknesses of from 0.1 to 20 micrometers.
These prior art plasma fabrication techniques are described in U.S. Pat. Nos. 5,366,770 of Wang, 5,260,105 of Wang, 5,364,562 of Wang, 5,157,015 of Snyder, Wang and Zhong, 5,120,703 of Snyder, Wang and Zhong, 5,213,851 of Snyder, Simmons and Wang, and 5,100,868 of Snyder, Hermann, Wang, Duan and Hao. The disclosure of each of these United States patents is hereby incorporated by reference into this specification.
It does not appear that any of prior art plasma coating processes is capable of readily producing coated products whose densities may be varied from about 50 percent to 100 percent; in most of the prior art plasma processes, the density of the coated film is from about 80 to about 90 percent.
Furthermore, the prior art plasma coating processes were not capable of producing oxide films with a substantially uniform surface morphology. Furthermore, the prior art processes were not capable of readily varying the surface morphology of the coated product.
In addition the prior art plasma coating processes do not produce columnar film growth, or vary the extent to which columnar film growth occurs. The prior art processes, in general, only produced agglomerate film growth.
The prior art plasma processes produced coated films which were substantially crystalline. They were not capable, however, of producing films which were substantially amorphous.
Furthermore, the prior art processes were not capable of producing coated films which would completely transmit visible light.
It is an object of this invention to provide a process which is capable of readily producing coated products whose densities may be varied from about 50 percent to 100 percent.
It is yet another object of this invention to provide a coating process which can produce oxide films with a substantially uniform surface morphology.
It is yet another object of this invention to provide a coating process which is capable of readily varying the surface morphology of the coated product.
It is yet another object of this invention to provide a coating process which is capable of producing columnar film growth and, additionally, varying the extent to which columnar film growth occurs.
It is yet another object of this invention to provide a coating process which is capable of producing coated films which are substantially amorphous.
It is yet another object of this invention to provide a process which is capable of producing coated films which will completely transmit visible light.
It is yet another object of this invention to provide a coating process adapted to deposit films on irregularly-shaped substrates, such as tubular substrates of fibers.
It is yet another object of this invention to provide a coating process which is capable of fabricating films which are electrically conductive and whose electrical conductivity can be varied.